Mozilla retires Firefox 4 from security support

Unnoticed in the Tuesday release of Firefox 5 was Mozilla's decision to retire Firefox 4, the browser it shipped just three months ago.

One traditional area of concern is add-on compatibility, a pain point known to longtime Firefox users when they've moved from one version number to the next.

Mozilla has retired Firefox 4 from security support, and is prompting users to upgrade to the new Firefox 5.

"The add-ons often aren't upgraded as fast as the browser itself," Computerworld reader Phillip Campbell wrote in a Tuesday e-mail after hearing about Firefox 5. "This leaves the users of Firefox often sitting and waiting for the extensions to catch up with the version before upgrading."

While Mozilla claims that 84% of the most widely used add-ons in its own download library are compatible with Firefox 5, it has acknowledged that others may not run on the newest version.

"Risk: LOW for AMO add-ons. HIGH for non-AMO add-ons," a note from a June 16 meeting said, referring to risks associated with launching Firefox 5 on schedule.

AMO, better known as Mozilla's Add-Ons, is the company's official download site for add-ons and browser themes. AMO is not the sole source of Firefox add-ons: Developers can market add-ons outside of the site. In that regard AMO is more like Google's Android Market than, for example, Apple's App Store.

Another reason why users may hesitate to upgrade to Firefox 5 is because they're running it in a business environment, where IT staff must usually test an updated application to ensure any changes have not created compatibility problems with other software.

Michael Kaply, a consultant who specializes in customizing Firefox and helping clients deploy the open-source browser, objected to the rapid-release schedule on corporate workload grounds.

"Companies simply can't turn around major browser updates in six weeks," said Kaply in a blog post Tuesday. "With security releases, there was a reasonable expectation that Web applications wouldn't break as a result of changes. With these releases, there is no such expectation. So a full test cycle needs to be run with every release."

By the time a company has tested Firefox 5, the next version -- now slated to ship in early August -- would be out, Kaply complained.

The corporate problem also came up in the Mozilla discussion thread.

"While I agree that longer [release] intervals would be better for corporate deployments ... I'm not at all certain it's the best thing for the Web or for Mozilla," said Mike Beltzner, a former director of Firefox who still contributes to the project. "We don't have the resources -- as a community -- to focus on their problems and on moving the Web forward."